hello!
I implemented the CG algorithm (with no preconditionning) for test
purposes, just to know how it works. i tried it with symetric but not
definite positive matrices. it SEEMS to work well, althought it is
established that it converges for symetric definite positive matrices
(Only?). Since it's a quite old algorithm, i gess this fact was
already noticed. So the question is: Why it's sayed that definite
positivenes (i'm not sure for the speling :/) is necessary for CG to
converge ?